Does the tachometer jumping seemed connected to the poor engine performance? I think you may have two separate problems, possibly bad instrument panel chip that drives the tach, and a separate engine performance problem.

With all your work, the problem may be somewhat unusual. Some suggestions to check:
1) Engine Coolant Sensor - If off this may cause poor performance, however there is an engine code for this, but perhaps the sensor is only off enough to cause poor performance.
2) Large air leak causing engine to overlean when you open throttle plate. This may be inconsistent w/ a good idle. Air leak usually causes high idle.
3) Valve timing & Ignition timing off due to mis-installation of timing belt. Check that crankshaft & camshaft both align to TDC together.
4) Intake air restriction or exhaust path restriction (burned, melted catalyst blocking exhaust path). I once had a Chevrolet do this due to leaded gas. It ran OK at low speed, but would barely accelerate. Check is to disconnect exhaust pipe from exhaust manifold to see if engine performance is dramatically improved. There is also a vacuum check for this condition. Check batauto.com site for tips on this vacuum testing procedure.

good luck

 

Thanks for the ideas, keep em comming!

Will take some days till i find time to work on the car again though.

@pahonda: its inside the distributor, so i already swapped it. Thnx though

 

Have you checked your O2 sensor? I have a '99 accord that had a problem with the O2 sensor. It would start and idle fine, but when you gave it a little gas, it was really doggy. I thought I was having a fuel problem...turns out I was..the O2 sensor was thinking there was too much fuel and cutting down fuel flow...

just a thought...hope this helps...

 

Hmm.. i´m not sure about that. The O2 sensor is the sensor in the exhaust? (sorry, but translating the technical terms is hard using the web..)

If so, you could be right. I disconnected it and the engine ran better. However the revcounter was still not working, so i dumped that idea. But if i´m dealing with two seperate problems as texashonda mentioned the o2-sensor could be one of them.
I will try to "borrow" a working one, to check this.

Thanks!